Applying sputum as a diagnostic tool in pneumonia: limited yield, minimal impact on treatment decisions

Chest. 2002 May;121(5):1486-92. doi: 10.1378/chest.121.5.1486.


Study objectives: We evaluated the role of sputum examination in the management of patients with community-acquired pneumonia (CAP) in a primary-care hospital without microbiologic laboratory facilities.

Design and interventions: A diagnostic strategy using regular collection of sputum samples, Gram staining in a local laboratory, and mailing of samples to a commercial laboratory for culture analysis.

Setting: A 200-bed primary-care hospital without subspeciality physicians.

Patients: One hundred sixteen consecutive patients with a diagnosis of CAP were prospectively evaluated during a 12-month period.

Results: Of 116 patients, 42 patients (36%) were capable of producing a sputum sample. Age > or = 75 years (odds ratio [OR], 0.4; 95% confidence interval [CI], 0.18 to 0.93) and prior ambulatory antimicrobial treatment (OR, 3.2; 95% CI, 1.2 to 8.4) were independent predictors of sputum production. A delay in collection and processing of sputum samples of > 24 h was present in 31% and 39%, respectively. A delay in collection yielded an increased number of Gram-negative enteric bacilli and nonfermenters (44% vs. 7%, p = 0.056). A delay in processing was associated with an increased number of Candida spp isolates (33% vs. 9%, p = 0.16). The overall diagnostic yield was low (10 of 116 patients, 9%) due to a limited number of valid samples (n = 23 of 42 patients, 55%) and a limited number of definitely or probably positive samples on Gram's stain and culture (n = 10 of 42 patients, 24%). Prior ambulatory antimicrobial treatment was associated with a reduction in diagnostic yield (14% vs. 56%, p = 0.09). The impact of diagnostic results on antimicrobial treatment decisions was minimal, with antimicrobial treatment directed to diagnostic results in only one patient.

Conclusions: We conclude that in this setting representative of primary-care hospitals in Germany, sputum had a low diagnostic yield and did not contribute significantly to patient management.

Publication types

  • Evaluation Study

MeSH terms

  • Adult
  • Aged
  • Aged, 80 and over
  • Anti-Bacterial Agents / therapeutic use
  • Community-Acquired Infections / diagnosis
  • Community-Acquired Infections / drug therapy
  • Female
  • Humans
  • Male
  • Middle Aged
  • Pneumonia, Bacterial / complications
  • Pneumonia, Bacterial / diagnosis*
  • Pneumonia, Bacterial / drug therapy
  • Prospective Studies
  • Pulmonary Disease, Chronic Obstructive / complications
  • Specimen Handling*
  • Sputum / microbiology*


  • Anti-Bacterial Agents